Exchanger



Feb. 12, 1963 R. E. JAPHET 3,077,088

FORCED FEED HEAT PUMP WITH COMPOUND COMPRESSION Filed March 21, 1962 OUTDOOR HEAT EXCHANGER INDuoR HEAT 4-6 32 43 Exclt-lzAgfi'ER I L 7 9 3| H.P. FLcA-r REG-UL)ATDR 7 (I7 n 13 ou'roook H T 53 EXCNANGER ACEUMULATQR PUMP 5 INDOQQ HEAT N 1 G.

4-6 EXQHANGER 2 3 (24) T W J, COOLING CYCLE 43 45 29 l6 9 H.P. FLOAT REG-U LATOR 7 (I1) ACCUzZI-LISATOR Pars; FIG. 2 RICHARD E. JAPHET HEATING CYCLE INVENTOR.

United States Patent Ofiice 3,77,88 Patented Feb. 12, 1953 3,tl77,i)88 FEED HEAT PUMP Wlllii CGMFOUND CGMPRESSIGN Richard E. .iaphet, Livingston, Nth, assignor to Worthington Corporation, Harrison, N..l., a corporation of Delaware Filed Mar. 21, 1962, Ser. No. 181,376 4 Claims. (Cl. 62-424) This invention relates generally to heat pumps and more particularly to a heat pump having combined compression and forced feed circulation cycles wherein the compressor means may be selectively staged for single or compound operation, as desired, dependent upon outdoor ambient temperatures.

In my co-pending U.S. application, Serial No. 107,181, filed May 2, 1961, a new and improved heat pump systern was described, characterized by the fact that the compressor functioned in a condensing or high pressure side cycle and a pump functioned in an evaporating or low pressure side cycle, which cycles were relatively independent but coacted by means of a common accumulator or the like separating means. This system, disclosed in full detail in said co-pending application, provides a substantial improvement over conventional flooded or direct expansion type heat pump systems. It operates at much greater eiiiciency (when used for heating and cooling) at intermediate periods of temperature and humidity; it permits minimum size and simplicity in components, including the elimination of complex multi-way valves; it eliminates slugging during the start-up and defrost cycles; it provides a relatively simple recovery means for dissolved or entrapped lubricant in the refrigerant fluid; and it provides a simplified energy conserving defrosting cycle.

The present invention is in the nature of an improvement and modification in the basic heat pump system set forth in said above mentioned copending application. In the basic system, there was illustrated a single refrigerant compressor means, and this is sufficient for basic operation and for many purposes. However, it is possible by means of the present improvement to increase the overall efiiciency of the system, to operate with more efiiciency during extremes of temperature and to adapt the heat pump for efiicient and economical use in climates having severe winter temperatures.

In the case of the single stage compressor system, where the ambient outdoor temperature is low, the heat required may easily exceed the heat available. In overcoming this, it has heretofore been necessary to overdesign the compressor capacity or the heat exchangers or both.

It is an object of the present invention, therefore, to provide a heat pump wherein there is greater flexibility of operation under varying extreme loads of heating and cooling, and wherein the compressed refrigerant can, when desired, be selectively operated at lower operating pressures and temperatures, giving greater efliciency for given sizes of compressor and heat exchanger components.

Still another object of the invention is to combine with a heat pump having a forced feed circulation cycle a means wherein a plurality of compressors may be selectively staged in series or in parallel, depending upon the season of the year in which the system is operating.

A further object of the invention is to provide a heat pump combining compression and forced feed circulation cycles with selective single or compound staged compressors, resulting in a system having a maximum simplification and maximum efficiency under extremes of ambient temperature relative to lower first cost than prior known heat pump systems.

Further objects and advantages of the invention will become evident from the following description with reference to the accompanying drawings in which:

FIGURE 1 is a diagrammatic sketch of the invention wherein the heat pump is being operated in its cooling cycle, with the outdoor heat exchanger operating as a condenser and a pair of compressors being staged in parallel.

FIGURE 2 is a diagrammatic sketch of the invention wherein the heat pump is being operated in its heating cycle, with the outdoor heat exchanger operating as an evaporator and a pair of compressors being staged in series.

FIGURES 1 and 2 illustrate diagrammatically arrangements of the same elements in the form of a heat pump in accordance with the present invention. They are distinguished in that the refrigerant temperatures, pressures and fiow paths between the elements differ for the respective cooling and heating cycles.

While in the heat pump system illustrated, one heat exchanger is shown in heat exchange relation with atmospheric air, it will be understood that such heat exchanger could be associated with other heat sink or heat source media, as will be understood by those skilled in the art, and that the corresponding heat exchanger best for the medium serving as the heat sink or heat source will be utilized. The same is true as to the second heat exchanger shown as having heat exchange relation with circulating water to be heated or cooled, and it will be understood that any liquid or gaseous media may be circulated therethrough. While a pair of compressors have been shown, it will be understood that any combination of two or more compressors or compressor units may be used without departing from the scope of the invention, providing they are suitably connected into the refrigerant circuit and suitably valved in accord with the teachings of the basic two compressor arrangement shown in the drawings.

GENERAL ARRANGEMENT OF THE HEAT PUMP Referring now to FIGURES 1 and 2, wherein the same parts will have the same character numerals, there is shown a pair of compressors A and B. The compressor A has a discharge outlet 2:: connected to a discharge line 3a disposed to receive hot compressed gaseous refrigerant from the compressor. Similarly, a compressor B has a discharge outlet 212 connected to a discharge line 1%. The discharge lines 3a and 3b intersect and are connected to the three conduits 4, 5 and 6, each of these conduits having their respective solenoid operated valves 7, 8 and 9 which can be manually or automatically controlled to provide that direction of flow in the system which will produce the desired cooling and heating cycles hereinafter described. The discharge line 3b is provided with a check valve 35, and the discharge line 3a is provided with a check valve 38, the function of which will later be more fully described.

Conduit 4 communicates with the inlet header it) of a first heat exchanger 11, which will be called for the purpose of present disclosure the outdoor heat exchanger, because it is disposed and located so that atmospheric air can be passed thereover, as by a fan 12, to permit good heat exchange relation to occur between the coils 13 of the heat exchanger and the air. The outlet header 14 of the first or outdoor heat exchanger communicates through connecting line 15, and common conduit 16, with a high pressure float regulator 17 in turn connected by connecting conduit 13 to collecting line 19 leading to accumulator 29. High pressure float regulators and accumulators are elements which are well known in the refrigeration art and require no further description.

The accumulator shall be sized sulficiently large to aoraoes 3 permit a proper separation of the gaseous and liquid refrigerant, which is delivered to the accumulator and shall be constructed to act as a high pressure receiver for storing the entire charge of the refrigerant as may be necessary during shutdown periods.

The compressors A and B have their suction inlets Zia and 2111, respectively, connected as by suction lines and 2259 to that portion of the accumulator 2t occupied by the gaseous refrigerant so that slugging of liquid is avoided during the operation of the compressor.

Conduit s communicates with the inlet chamber 23 of the second heat exchanger 554 which is termed for the purposes of the present description as the indoor heat exchanger because it will be disposed at an enclosed point such that either a liquid or gas may be circulated over the coils 25 to provide means for transferring heat or abstracting heat depending on the cycle in operation at the time. This is accomplished in the present form of the invention by passing liquid through inlet 26 and removing it by outlet 27. Heat exchangers for this purpose are well known in the air conditioning and refrigeration art and need not be more precisely described.

The outlet chamber 28 for the second or indoor heat exchanger 24 is also connected through return line 29 to the common line 16 which communicates with the high pressure float regulator 17.

FIGURES l and 2 show that the conduits l and 2% are provided with check valves as at 3% and 31 respectively so that the flow of refrigerant fluid through the outdoor and indoor heat exchangers will be unidirectional, 'a specific characteristic of the operation of the present invention, regardless of the particular cycle in operation.

FIGURES l and 2 also show that lines 15 and 29 communicate through lines 33 and 32, respectively, di rectly to collecting line it? and, depending on the operating cycle which calls for the setting of the control valves 34 and 35 for the respective lines 32 and 33, refrigerant gas and liquid from one or the other of the heat on changers It or 24 can by-pass the high pressure float regulator 17 and be passed directly to the accumulator 26.

The operation of the control valves '7, 8, 9, 3d and 35 may be manual or automatic, and many different types of programming control systems could be used.

Pumping System In order to provide the positive or force feeding circulation of refrigerant liquid to the respective indoor and outdoor heat exchangers in the various cycles hereinafter described, where the heat exchanger is not receiving hot compressed gaseous refrigerant, a pump dd is provided having its suction connected by line 41 to the portion of the accumulator 2G in which the liquid refrigerant accumulates. The pump discharges through common discharge line 42 to the connecting conduits 43 and 44, which are in turn connected to the conduits 4 and 6 leading to the outdoor and indoor heat exchangers 1i and 24. It should be mentioned that the presently described system is not restricted in use to any particular refrigerant material. It will function with those gases such as Freon which are ordinarily employed for refrigerating purposes.

As shown in PiGURES l and 2 connecting conduits t3 and 4d are provided with check valves 45 and 26, respectively, which check valves will direct the flow of refrigerant liquid, depending on the settings of control valves 7 and 9.

Check valves 3d and 31 also operate similarly, depending on the settings of control valves 34 and 35.

in both the case of check valves 3d and 33 and ch ck valves 45 and es, the pressure of the refrigerant will pressurize one or the other of the check valves so that ilow will occur through that check valve which does not have the pressure acting against its discharge side.

The valves 34 and 35 also permit the inclusion of a defrosting cycle which is accomplished through the defrosting conduit 5 connected from the common discharge line 3 to a point downstream of the solenoid operated valve '7 and the check valve in order the the compressors A and B may be sclectively connected for either single stage, parallel operation, or compound stage, series operation, a compound staging lay-pass line 39 extends from the discharge line 3a to the suction line 22b. interposed in this by-pass is a solenoid operated valve 47, and this valve may either be manually operated or may be activated to open or closed position by automatic programming means.

While it has not been shown, it is to he understood that an i-tnercooler of known type could be placed in the compound staging by-pass line 33 to reduce the temperatures of the refrigerant gas between the first and second stages of the compound system. Cooling of the refrigerant at this intermediate stage of compression is highly desirable. Without at least some means of cooling, the compressed gas on emerging from the second stage would ordinarily have a sufiiciently high temperature to cause damage or thermal deterioration to flow control elements into which it passed.

Oil Recovery Mean The heat pump with a force feed pumping arrangement as above described is particularly characterized by the fact that no oil can accumulate in the system in any of the heat exchangers or in any piping traps, as occurs in heat pump arrangements now known in the prior art. Oil collects at only a single point in the system, namely, the accumulator 2t and this permits a unique, simple method of oil recovery in that oil-rich refrigerant may be sampled from the downstream side of the pump 4th by a relatively small bleed line 59, having a solenoid operated valve 51 therein which can be maintained open during the cycles which include compressor operation.

The oil-rich refrigerant, sampled through the bleed line 5% is evaporated by wrapping the bleed line as at 52 around one of the hot lines, such as the discharge line 3a from the compressor A. This evaporated refrigerant in gaseous form, containing small particles of oil, can be returned to the compressor by connecting the outlet of the line Ell to the suction inlet line 22a leading to the suction of the compressor A.

Since there is a pressure ditlerence between the dis-- charge side of the pump 4% and the suction side of the compressor A, a very effective nonciogging, easily regulated, oil recovery system will be incorporated in the heat pump. A control for sensing superheat in line 54) is provided as at 53 and will be utilized to regulate the how of oil-rich refrigerant throu h line 5%.

COOLING CYCLE (Compressors A and B Arranged in Parallel) Specific reference is now made to PEGURE l of the drawings, illustrating the system of the invention as being used for a cooling cycle. This is normally for summer operation when outdoor temperatures are relatively high and it is desired to lower the temperature in any enclosure to which the system is applied.

The compressors A and B, the pump 4% and the fan 12 are placed into operation; valves '7, 34 and 51 will be opened; and all other positively operated valves will be closed. This includes the solenoid operated valve 47 in the compound staging by-pass line 39. Pressures in the system are such that check valves 3'7, 36 and 33 are opening in the downstream direction of flow. in the case of checlt valve 37, gaseous refrigerant is being admitted from the accumulator 25 to the suction side fill) of the compressor 3. In the case of check valve 36, hot compressed refrigerant is being passed from the outlet 2b of the compressor B to the common line 3]). In the case of the valve 38, refrigerant from the discharge outlet 2a of the compressor A is being passed into the common line 3b. The compressors A and E are thus in parallel apnoea operation, both accepting gaseous refrigerant from the accumulator 2i and passing hot compressed gaseous refrigerant to the common conduit l connected to the inlet header 1% of outdoor heat exchanger 11. In the outdoor heat exchanger 11 the hot compressed gaseous refrigerant will be condensed to provide a hot liquid refrigerant which will collect in the outlet header 1d of the outdoor heat exchanger ill.

The hot liquid refrigerant passes from the outlet header 14 through lines 15 and 16 to the high pressure float regulator 17 which serves to pass or meter liquid of which a portion flashes into gas which moves through lines 18 and 19 to the accumulator 20. This mixture of relatively cold gas and liquid refrigerant mixes with other relatively cold gas and liquid refrigerant which is r turned from the indoor heat exchanger as hereinafter described.

In the accumulator 20, which is properly sized, the gaseous and liquid refrigerant separate so that a gas layer occupies the upper portion of the accumulator and the liquid layer occupies the lower portion of the accumulator, as is indicated by the dotted line in FIGURES 1 and 2.

Since the suction lines 22a and 22b of the compressors are connected to the upper portion of the accumulator which holds the gaseous refrigerant, only gas passes through the suction lines 22a .and 22b, and the suction inlets 21a and 21b of the compressors, Where it is once again compressed to repeat the condensing cycle.

The relatively cold liquid refrigerant in the accumulator 26 is also pumped with positive pressure to the indoor heat exchanger 24 by means of the pumping system above described. Thus, pump 46 receives liquid through the line i1 and discharges the refrigerant liquid through line 42. Due to the fact that hot compressed gaseous refrigerant is passing through conduit i, the check valve 45 is prevented from opening, and this discharged liquid refrigerant under pressure must be delivered through conduit 44 and check valve 46 to the conduit 6 connected to the inlet header 23 of the indoor heat exchanger 24. At the indoor heat exchanger, the liquid refrigerant is passed therethrough into heat exchange relation with fluid which is delivered through line 26 and removed by line 27, so that the cold liquid refrigerant is partially evaporated as it cools the fluid being passed through the indoor heat exchanger. This cooled fluid media as it leaves line 27 may be passed to any suitable point of use.

Refrigerant collected in the outlet header 23 of heat exchanger 24 will be part gas and part liquid, because the pump supplies a greater quantity of refrigerant than is required. This is advantageous because the inner surface of the tubes of the heat exchanger will, under these conditions, be continually wetted, thereby increasing the efficiency of the heat exchanger.

This mixture of gaseous and liquid refrigerant will be passed from the outlet header 28 through the lines 25 32 and control valve 34, to the collecting line 1& where it joins with a like mixture of gas and liquid from the high pressure float regulator 17 as it flows through line 19 to the accumulator 2% connected thereto. This pumping circulation cycle will operate continuously to provide the desired cooling as long as the compressor continues to operate with the valves set for the cooling cycle as above described.

HEATING CYCLE (Compressors A and B Arranged in Parallel) Referring again to FIGURE 1 the system may be adjusted for providing heat in a cold climate or atmosphere.

To accomplish this, compressors A and B, pump 44. and fan 12 are placed in operation. Positively operated valves 34, '7, 8 and 47 are closed. Valves 9, 35 and 53. are opened. Pressures in the system are such that cheer; valves 37, 3t; and 33 are opening in the downstream direction of flow. In the case of check valve 37, gaseous refrigerant is being admitted from the accumulator 26 to the suction side 21b of the compressor B. in the case of valve 3-6, hot compressed refrigerant is being passed from the outlet 2b of the compressor B to the common line. In the case of valve 38, refrigerant from the discharge outlet Za of the compressor A is being passed into the common line.

The comprmsors A and B are thus again in parallel operation, both accepting gaseous refrigerant from the accumulator 2d and passing hot compressed gaseous refrigerant to the common conduit 6. The latter conduit directs refrigerant to the inlet header 23 of the indoor heat exchanger 24 where it gives up heat to the medium to be heated. This Indium as mentiond may be water brought into the heat exchanger 24 through inlet 26 and discharged through outlet 27 to the desired point of use in heated condition.

The release of heat to the media to be heated causes the gas to condense and provide liquid refrigerant, which liquid refrigerant passes through the outlet header 2?: of

the heat exchanger 24 through line 29 and check valve 31 to the common line 16 leading to the high pressure float regulator 17.

In high pressure float regulator 17 the liquid flashes and during expansion cools so that relatively cool gas and liquid refrigerant is then led to the accumulator 20 through the line 19. This mixture of relatively cold gas and liquid refrigerant mixes with other relatively cold gas and liquid refrigerant which are returned from the outdoor heat exchanger 11.

In addition to the heat of compression, heat is also drawn from the heat source in contact with the outdoor heat exchanger 11 by force feeding refrigerant to the latter. This is accomplished by means of the pumping circuit. Thus, pump 40 through line 41 draws cold refrigerant from the liquid layer of refrigerant in accumulator 2t! and discharges it through discharge line 42. Since the hot compressed gaseous refrigerant is being discharged to conduit s, the pumped fluid cannot pass through check valve 45 and instead passes through check valve 45 in conduit into conduit 4 connected thereto, where it is forced to the inlet header ill of the outdoor heat exchanger 11.

As it passes through coils 13 of the outdoor heat exchanger lll, the liquid refrigerant, which will always be colder than the heat source, will pick up heat from the heat source and then from the outlet header 14 it Will be passed to lines 15, 33 and control valve 35 to collecting line 19 and thence to the accumulator 29 Where it mixes with the mixture of gas and liquid refrigerant returning from the high pressure float regulator 17 to the accumulator The mixtures passed to the accumulator separate and are recirculated through the system.

HEATING CYCLE (Compressors Arranged in Series) With reference to the heating cycle shown in FIGURE 2, the valves are suitably manipulated by manual or automatic means to place the cycle into operation. The pump ill and fan 12 are placed in operation. Positivly operated valves 34, '7 and 8 are closed. Valves 9, 35 and 4 7 are opened. Hot compressed refrigerant gas from the discharge outlet 2:: of the compressor A will move through the compound staging bypass line 39 and will enter the suction inlet 23b of the compressor B at increased temperature and pressure. The pressure in the line 22b will bias the check value 37 into closed position, preventing dumping of the hot compressed refrigerant back into the accumulator. Check valve as will be biased open to permit passage of the second stage compressed refrigerant from the discharge side 2b of the compressor B into the line 6. The check va.ve 3d, influenced by the greater pressure in the second stage downstream side of the compressor B, will be biased into a closed position.

Therefore, gaseous refrigerant from the accumulator Z 26 will have passed in series through the compressors A and B, acting as a first and second stage. This multistaging causes the refrigerant to be more highly compressed and thus function more efficiently than was the case where the compressors were used in parallel single stage operation.

The said highly compressed gaseous refrigerant will be passed by conduit 6 to the inlet harder 2-3 of the indoor heat exchanger 24-, where it gives up heat to the medium to be heated as, for example, water brought into the heat exchanger 24 through inlet 26 and discharged to the desired point of use through outlet 27 in the heated condition.

The release of heat to the media to be heated causes the gas to condense to provide liquid refrigerant, which liquid refrigerant passes through the outlet header 28 of the heat exchanger 24 through line 29 and check valve 31 to the common line 16 leading into the high pressure float regulator 17.

in high pressure float regulator 17 the liquid flashes and during the expansion cools so that relatively 0001 gas and liquid refrigerant is then led to the accumulator 29 through the line 19. This mixture of relatively cold gas and liquid refrigerant, as has been mentioned in the description of the cooling cycle, mixes with other relatively cold gas and liquid refrigerant which is returned from the outdoor heat exchanger 11 as hereinafter described. By reason of the size of the accumulator 2", the refrigerant mixture separates to provide a gaseous layer and liquid layer of the refrigerant in intimate contact with each other.

in addition to the heat of compression from the compound staged compressors, heat is also drawn from the heat source in contact with the outdoor heat exchanger ill by force feeding refrigerant liquid to the outdoor heat exchanger. This is accomplished by means of the pumping assembly. Thus, pump ll? through line 41 draws cold liquid refrigerant from the liquid layer of the refrigerant in the accumulator Eli and discharges it through discharge line Since hot compressed gaseous refrigerant is being discharged to conduit 6, the pumped fluid cannot pass through check valve as and instead passes through check valve 45 in conduit 43 into conduit 4 connected thereto, where it is forced to the inlet header lift of the outdoor heat exchanger 11. As it passes through coils 13 of the outdoor heat exchanger 11, the liquid refrigerant, which will always be colder than the heat source, will piclt up heat from the heat source and then from the outlet header 14 it will be passed to lines 15, 33 and control valve 35 to collecting line H and thence to the accumulator 2t"; where it mixes with a mixture of gas and liquid refrigerant returning from the high pressure float regulator l? to the accumulator 2d. The mixtures passed to the accumulator separate and, as above described, recirculate through lines 22a and 41 to the compressor A and pump, respectively, to repeat the cycle.

DEFROST CYCLE AND lNTERMEDlATE COOLXNG CYCLE The defrost cycles and intermediate cooling cycles, of which the disclosed invention is capable, have been more fully described as to operation in my above mentioned co-pending application Serial No. 107,181. Since the op eration of these cycles is the same with plural compressors in single or compound staging, as is the case or" the single compressor, the operation of these cycles will not be repeated herein, and reference is made to the complete operation as set forth in said co-pending application.

I have provided therefore a novel heat pump apparatus which is particularly characterized by a wider operating range for accomplishing either heating or cooling. It may readily be appreciated by one skilled in the at that a system as presently disclosed offers many advantages from the standpoint of both versatility and economy.

Notably, the multiple compression B1 angernent permits the heat pump to function at full capacity and at maximum etlioiency regardless of the air conditioning load imposed thereon.

For example, to assure a high efiiciency in the compressor system, the compression ratio is preferably held to a low value. As the compression ratio increa es, the volumetric efiiciency of the system will normally be decreased. With the instant arrangement, however, it is possible to realize a higher overall volumetric efliciency than is ordinarily obtainable.

While in the description and drawings, there has been shown and described the preferred embodiment of the invention, it is to be understood that variations may be made in the construction and arrangement of parts without departing from the spirit and scope of the invention as defined by the claims.

What is claimed is:

1. In a heat pump, a plurality of heat exchange means, a common sepana-ting means for storing and separating gaseous and liquid refrigerant, means connecting the downstream side of each of said heat exchange means to said separating means, a compression means, said compression means having its suction connected to said common separating means and disposed to discharge hot compressed gaseous refrigerant interchangeably and selectively to the upstream side of at least one of said heat exchange means, and a pump circulation circuit having the suction connected to said separating means to receive liquid refrigerant therefrom and to force feed an excess of liquid refrigerant to the upstream side of at least one other of said heat exchange means not receiving hot compressed gaseous refrigerant from said compression means, said compression means comprising a plurality of separate compressor units, and means for selectively connecting said compressor units in fluid circuit in parallel, single stage operation or series, compound stage operation.

2. in a heat pump, a plurality of heat exchange means, a common separating means for storing and separating gaseous and liquid refrigerant, means connecting the downstream side of each of said heat exchange means to said separating means, a compression means, said com pression means having its suction connected to said common separating means and disposed to discharge hot coll pressed gaseous refrigerant interchangeably and selec tively to the upstream side of at least one of said heat exchange means, and a pump circulation circuit having the suction connected to said separating means to receive liquid refrigerant thereform and to force feed an excess of liquid refrigerant to the upstream side of at least one other of said heat exchange means not receiving hot compressed gaseous refrigerant from said compression means, said compression means comprising a plurality of separate compressor units, each of said compressor units having its upstream, suction side connected to the gas storage portion of said common separating means, and means for selectively connecting said compressor units in iluid circult in parallel, single stage operation or series, compound stage operation.

3. In a heat pump, a plurality of heat exchange means, a common separating means for storing and separating gaseous and liquid refrigerant, means connecting the downstream side of each of said heat exchange means to said separating means, a compression means, said compression means having its suction connected to said common separating means and disposed to discharge hot compressed gaseous refrigerant interchangeably and selectively to the upstream side of at least one of said heat exchange means, and a pump circulation circuit having the suction connected to said separating means to receive liquid re *igerant therefrom and to force feed an excess of liquid refrigerant to the upstream side of at least one other of said heat exchange means not receiving hot compresse gaseous refrigerant from said compression means,

ac /aces said compression means comprising a plurality of separate compressor units, each of said compressor units having its upstream suction side connected by a supply conduit to the gas storage portion of said common separating means and its discharge side connected to a common discharge conduit, and means for selectively connecting said compressor units in fluid circuit in parallel, single stage operation or series, compound stage operation, said last means comprising a fluid by-pass conduit connecting the discharge side of one compressor unit to the intake side of its next adjacent, upstage compressor unit, a positively operated shut-off valve in each of said lay-pass conduits, a first check valve means in the supply conduits of all but the first of said compressor units, a second check valve means in the discharge side of all but the first of said compressor units, and a third check valve means in said common discharge conduit, said third means comprising separate check valves positioned between the connections of the discharge side of each of said compressor units to said common discharge conduit.

4. In a heat pump, a plurality of heat exchange means, a common separating means for storing and separating gaseous and liquid refrigerant, means connecting the downstream side of each of said heat exchange means to said separating means, a compression means, said compression means having its suction connected to said common separating means and disposed to discharge hot, compressed, gaseous refrigerant to a common conduit, valve means in said common conduit for selectively and interchangeably delivering said hot, compressed fluid to the upstream side of at least one of said heat exchange means, and a pump circulation circuit having its suction connected to said separating means to receive liquid refrigerant therefrom and to force feed an excess of liquid refrigerant to the upstream side of at least one other of said heat exchange means not receiving hot compressed gaseous refrigerant from said compression means, said compression means comprising a plurality of separate compressor units, each of said compressor units having its upstream, suction side connected by a supply conduit to the gas storage portion of said common separating means and its discharge side connected to said common discharge conduit, and means for selectively connecting said compressor units in fluid circuit in parallel, single stage operation or series, compound stage operation, said last means comprising a fluid by-pass conduit connecting the discharge side of one compressor unit to the intake side of its next adjacent, upstage compressor unit, a positively operated shut-oii valve in each of said lay-pass conduits, a first check valve means in the supply conduits of all but the first of said compressor units, a second check valve means in the discharge side of all but the first of said compressor units, and a third check valve means in said common discharge conduit, said third means comprising separate check valves positioned between the connections of the discharge side of each of said compressor units to said common discharge conduit.

References Cited in the file of this patent UNITED STATES PATENTS 2,693,092 Labolle Nov. 2, 1954 2,724,240 Sloan Nov. 22, 1955 2,869,335 Worden Ian. 20, 1959 

1. IN A HEAT PUMP, A PLURALITY OF HEAT EXCHANGE MEANS, A COMMON SEPARATING MEANS FOR STORING AND SEPARATING GASEOUS AND LIQUID REFRIGERANT, MEANS CONNECTING THE DOWNSTREAM SIDE OF EACH OF SAID HEAT EXCHANGE MEANS TO SAID SEPARATING MEANS, A COMPRESSION MEANS, SAID COMPRESSION MEANS HAVING ITS SUCTION CONNECTED TO SAID COMMON SEPARATING MEANS AND DISPOSED TO DISCHARGE HOT COMPRESSED GASEOUS REFRIGERANT INTERCHANGEABLY AND SELECTIVELY TO THE UPSTREAM SIDE OF AT LEAST ONE OF SAID HEAT EXCHANGE MEANS, AND A PUMP CIRCULATION CIRCUIT HAVING THE SUCTION CONNECTED TO SAID SEPARATING MEANS TO RECEIVE LIQUID REFRIGERANT THEREFROM AND TO FORCE FEED AN 